Process for formation of highly uniform arrays of nano-holes and nano-pillars
A photolithography method of patterning photoresist involves disposing a two-dimensional array of focusing particles of spherical or other shape on the photoresist and illuminating the particles on the photoresist to generate deep, sub-wavelength patterns on the photoresist. When developed, a positive photoresist layer generates a two-dimensional array of micro- or nano-holes on the developed photoresist. When developed, a negative photoresist layer generates a two-dimensional array of micro- or nano-pillars on the developed photoresist.
1. A method of patterning a photoresist, comprising:
(a) disposing a two-dimensional array of substantially spherical particles on a photoresist layer on a substrate;
(b) illuminating the particles on the photoresist layer while focusing the illumination through the particles to respective regions of the photoresist layer beneath the particles with each region forming a sub-wavelength pillar having a diameter dimension that is less than the wavelength of the illumination; and
(c) developing the photoresist,
wherein the photoresist layer comprises a negative photoresist so that developing of the photoresist leaves a two-dimensional array of micro- or nano-pillars on the developed photoresist.
2. The method of claim 1 including removing the particles before or after developing the photoresist layer.
3. The method of claim 1 wherein the micro- or nano-pillars have an undercut shape.
4. The method of claim 1 wherein the particles have a diameter in the range of 0.5 microns to 5 microns.
5. The method of claim 1 wherein the particles comprise silica or polystyrene.
6. The method of claim 1 wherein the illumination comprises UV light.
7. The method of claim 6 wherein the UV light has a wavelength of 200 to 500 nm.
8. The method of claim 1 including self assembling the particles on the photoresist.
9. The method of claim 1 wherein the two-dimensional array of sub-wavelength features has a periodicity corresponding substantially to the particle array.
10. The method of claim 1 including depositing a material on the developed photoresist layer and then removing the developed photoresist layer.
11. The method of claim 1 wherein the particles are disposed in a hexagonal close packed array.